MEASUREMENT OF THE PHASE CENTERS OF ANTENNAS

Abstract : There are many antennas, including the logperiodic and log-spiral antennas, that do not have a unique phase center. For these antennas an 'apparent phase center' is defined over a limited range of space surrounding the antenna. A measurement technique has been developed that will permit automatic plotting of modified phase patterns from which the effective position of this 'apparent phase center' may be determined. This technique requires the use of only standard antenna pattern recording equipment and a detector which is sensitive to the amplitude and to the phase of the radiated field of the particular antenna under consideration. Deviations of these patterns from a unit circle on a polar plot or straight line on a rectangular plot (or as a modification, from the amplitude pattern), may be interpreted from curves supplied, to show the position of the phase center with respect to the known center of rotation used to obtain the patterns. (Author)